1. Field of the Invention
The invention pertains to a cartridge plunger with at least one gas evacuation opening and at least one gas evacuation element covering the cartridge plunger opening.
2. Prior Art
A cartridge plunger of this kind is known from DE 298 00 594 U1. In this case, a gas evacuation hole in the plunger is covered by a filter element, designed as a micropore filter, which is installed in a pocket formed in the plunger. Due to this filter element, the air located in the cartridge between the plunger and the filler material can escape when the plunger is pressed into the cartridge, but any discharge of the filler material will be prevented. However, gas evacuation devices of this kind are only conditionally suitable for low-viscosity resins, since the resin can diffuse through the filter element during storage. Thus, the result may be undesirable leakage.
In addition, plungers with special gas evacuation valves are known, which are actuated by specially shaped plunger insertion pins when inserting the plunger into the cartridge. However, the manufacture of these plungers is rather complicated, and is thus associated with correspondingly greater expense. The valve technology is thus too expensive, especially for smaller and low-cost cartridges.
It is the purpose of the invention to create a simply-designed and low-cost cartridge plunger which will allow dependable gas evacuation and at the same time will prevent any undesirable leakage of the filler material.
This problem is solved by a cartridge plunger with at least one gas evacuation opening and at least one gas evacuation element covering the cartridge plunger opening that is characterized in that the gas evacuation element is at least one cover disk which forms a labyrinth path running transverse to the plunger axis and being located between the contact surface of the cover disk facing the gas evacuation opening and a corresponding contact surface on the cartridge plunger
In a further refinement of the invention the cartridge plunger in that to form the labyrinth path, the contact surface of the cover disk and/or the contact surface on the cartridge plunger has a specified surface roughness. In a particular refinement, the contact surface of the cover disk and/or the contact surface on the cartridge plunger has a surface roughness between 10 and 50 xcexcm.
According to the invention, the cartridge plunger can be characterized in that there is a recess to hold the cover disk located in the front surface facing the cartridge inside. Also, the contact surface can run conically inward in the direction of the gas evacuation opening.
Further, the cartridge plunger can be characterized in that at the upper edge of the recess can have an annular flange to provide a snap attachment of the cover disk within the recess. Also, the cover disk can be flexible. In addition, the cover disk can consist of a soft plastic.
The invention pertains to a cartridge plunger with at least one gas evacuation opening and at least one gas evacuation element covering the cartridge plunger opening. For a simple and dependable gas evacuation and to prevent any undesirable leakage of the filler material, the gas evacuation element is at least one cover disk which forms a labyrinth path running transverse to the plunger axis, said path being located between the contact surface of the cover disk facing the gas evacuation opening and a corresponding contact surface on the cartridge plunger.
The cartridge plunger according to this invention is characterized in that a labyrinth path is formed between the cover disk and the plunger, running transverse to the plunger axis, through which the air located between the plunger and the filler material can escape when pressing the plunger into the cartridge, but such that the filler material located in the cartridge will be held back.
In one particularly efficient embodiment of the invention relative to manufacturing engineering, a cover disk is used made of a soft plastic with a rough contact surface that comes to rest against a smooth contact surface of the plunger. Thus, in this simple manner a filter or labyrinth path is created between the rough contact surface of the cover disk and the smooth contact surface on the plunger.
However, in place of the rough contact surface of the cover disk, the contact surface on the plunger itself, or both the contact surface as well as the contact surface of cover disk and plunger, can also be designed as a rough surface.
The surface roughness can be adapted to particular requirements continuously and at low cost by selection of the particular material or by processing of the surface. For example, a surface roughness of 10 to 50 xcexcm, preferably 30 xcexcm, has proven to be particularly useful for resinous filler materials.